The present invention relates to a method of obtaining a highly conductive arc-resistant electrical contact pad on a metal body, and more particularly to such a method which includes substantially simultaneously joining the contact pad to the metal body and shaping the combination of the contact pad and the metal body.
In the electrical industry, electrical contacts, or contact pads, of many forms are needed. For example, in the transmission and distribution of electrical power, various protective equipment devices, e.g., switches, cut-outs, fuses, etc., are employed. Such devices generally include electrical contacts which must be highly electrically conductive and also must be capable of opening and closing while carrying a current load. These highly electrically conductive contacts should also be resistant to arcing, i.e., resistant to erosion, as it is well known that arcing generally results when electrical contacts are opened and closed under a current load.
Conventional techniques to provide such highly conductive arc-resistant electrical contacts, or contact pads, have been satisfactory in many respects. However, such conventional techniques have several disadvantages both in the processing and in the resultant contact. For example, in the case of a cut-out structure, such as the one disclosed in U.S. Pat. No. 3,377,447, entitled, "Load Break for Open Type Cut-Outs," issued Apr. 9, 1968 to Hermann et al., one conventional technique to obtain an electrical contact is to selectively silver plate the appropriate portion(s) of the necessary metal components of the cut-out structure. Typical plating thicknesses for such applications are generally in the range of 0.0002 to 0.0005 inches. Such thicknesses are often insufficient to provide a desirable degree of arc-resistance. However, satisfactory plating thicknesses greater than the foregoing are difficult to obtain because such thicknesses generally are difficult to maintain uniformity. Also, such thicknesses often result in poor metallurgical qualities. Further, from a processing or manufacturing viewpoint, accurate selective plating of a portion of a surface of a metal body is difficult to achieve because it requires much handling of parts, including masking thereof. Also, such selective plating is undesirably time consuming.
Accordingly, it is a common industrial practice to plate the entire surface of the involved metal component, including the area which is to serve as the electrical contact or contact pad. Such an extensive plating practice is quite undesirable in view of the considerable expense of contact materials, such as silver. Also, in conventional plating techniques, if it is necessary to shape the involved component and its plated contact pad, such shaping is generally provided after the plating step. From a manufacturing standpoint, this may be undesirable as the typical plating thicknesses of 0.0002" to 0.0005" are susceptible to damage, e.g., scratching during such shaping.
Accordingly, it is a general object of this invention to provide a method of obtaining a highly conductive arc-resistant electrical contact pad on a portion of a surface of a metal body.
Another object of this invention is to provide such a method which includes substantially simultaneously joining such a contact pad to the metal body while shaping the combination of the contact pad and the metal body.
Another object of this invention is to provide such a highly conductive arc-resistant electrical contact pad on a portion of a surface of a metal body.